Portable information terminals such as cellular phones and PDAs (Personal Digital Assistants) have conventionally employed user interfaces using keypads, which are composed of a plurality of buttons for input of numbers and characters and direction buttons.
In recent years, display units of portable information terminals have been made capable of displaying graphics and usable in two-dimensional manner. In nowadays when functions of portable information terminals are brought near to those of computers with operations of the terminals made complex, methods of performing operations for desired functions with use of the menu keys and other function keys as direction keys have been becoming difficult to employ as a method of input into such portable information terminals because the operations cannot be performed easily. Accordingly, demands have been increasing for pointing devices that can be operated like mice and touch pads used in computers.
In such a background, there has been proposed a method of extracting change in a contact surface by observing, by an imaging element, a pattern of a fingertip or the like in contact with a pointing device. There has been also proposed a method of converting a motion of a fingertip into input signals by illuminating a contact surface with a light source, imaging a pattern of the contact surface on an imaging element by lenses, and detecting change in the pattern.
For instance, such a pointing device is disclosed in WO 2006/011711 A1 (Patent Literature 1).
The pointing device has a cover glass, a light source part, and a light receiving part, and the light source part is composed of a light source and a light source guide. Light emitted from the light source is reflected at a specified angle and is then projected onto the cover glass. The light projected onto the cover glass and having penetrated an upper surface of the cover glass is reflected by a surface of a finger. The light reflected by the surface of the finger penetrates a back surface and is projected onto the light receiving part. The light receiving part is composed of a reflecting mirror, a condenser lens and an optical image sensor. The light reflected by the reflecting mirror is imaged by the condenser lens so as to be provided to the optical image sensor. As the optical pointing device, there are proposed a device filled with air as medium between the optical components and a device employing an optical waveguide for minimizing the loss of the light therebetween.
Another optical pointing device is disclosed in WO 2006/019218 A1 (Patent Literature 2).
The optical pointing device has a first waveguide, a second waveguide, an image sensor, a cover glass, and a light source part. The first waveguide has a first reflecting surface and a first planoconvex lens that form a single body, and the second waveguide has a second planoconvex lens and a second reflecting surface that form a single body.
Light emitted from the light source is projected onto an object and is reflected by the object. The light reflected by the object is refracted by the first reflecting surface and the refracted light is then condensed while passing through the first and second planoconvex lenses. The light having passed through the first and second planoconvex lenses is refracted by the second reflecting surface and is imaged on the image sensor. Spaces between the optical components are filled with air as medium.
Still another optical pointing device is disclosed in WO 2005/088435 A1 (Patent Literature 3).
The optical pointing device is composed of a light source for emitting light to an object, an object plane for receiving the light emitted from the light source, an optical lens for reflecting an image from an image acquisition surface, and an optical sensor for receiving the image reflected from the optical lens and converting the image into an electrical signal. Spaces between the components are filled with air as medium.
Citation List
Patent Literature                Patent Literature 1: WO 2006/011711 A1        Patent Literature 2: WO 2006/019218 A1        Patent Literature 3: WO 2005/088435 A1        